Sunday, June 24, 2012

Sweating...

Following my prediction that we would "enjoy" a linear progression of ever-higher temperatures, a prediction based on the uncharacteristically mild winter we had, we had an August heat wave in June. When the temps are 90+, it becomes difficult to opt for a few hours in the temperature accentuating hangar (it makes hot days hotter and cold days colder) over spending an evening at home basking in more temperate, albeit artificial, conditions.

So after spending a week in air conditioned bliss, why is the subject of this post "Sweating?"

I'll get to that.

And to be fair, it was easy to opt to stay at home rather than work on the airplane because I had a part on order. As you may recall, I was working on the cable that will open and close the door that blocks heat from the aft side of the engine radiator from pouring into the cockpit. Cold in the winter? Pull the cable, open the door, get warm(er). Hot? Push the cable, close the door.

I had gotten to the point where I needed a rod bearing, but I couldn't find it. There was a bag that was supposed to have four of them in it, but they were all gone, probably having been used on other parts of the plane. They're cheap and I needed to order some other stuff from Van's anyway, so I ordered one on Sunday afternoon.

It finally arrived on Friday.

The first order of business on Saturday morning, then, was to use the newly procured part to finish that cable. First step: screw the rod bearing as far as it will go into the metal tube that will support it. Then tighten the jam nut hard up against it.

Jam nut? I couldn't find any of those either!

Pete: "Have you checked in the engine kit parts?"

Me: "Of course not. I'm working on the Finish Kit - why would it be in the Eng.... oh, yeah, here it as. And here's the rod bearing, too."

An ignominious beginning.

With the parts in hand, I did the measuring and bending of the control wire shown below. When that's done, the hooped end of the wire gets shoved up into the metal tube that holds the fully jammed in rod bearing. Then a cotter pin gets shoved through a hole in the tube and through the hoop in the wire.

I'm nothing if not pessimistic, and I had dire concerns over whether I'd be able to get that hoop into the tube far enough to get the cotter pin to fit through. Sure enough, I got it to where I could see the hoop through the hole in the side of the tube, but I just couldn't get the hoop to move the 1/32" further in that it would need to go to get the pin through it. I tried sticking an awl into the hole to force the wire further into the tube. No go. I tried pushing while swearing. I tried swearing while pushing. I even tried swearing before, during, and after pushing.

No good.

I am beginning to lose my faith in the power of swearing.

The problem turned out to be my slavish devotion to the instructions. Threading the rod bearing all the way into the tube as far as it would go had positioned it such that there was no room for the wire to go.

I had to let it out a few threads.

The cushion clamps that hold the cable housing in place are somewhat loosely mounted on the engine mounts (I don't know why - using the bolts called out by Van's, there's still a little looseness once the bolts are as tight as they can get), so a piece of safety wire is specified as a way to keep the cable housing from slipping.

Meanwhile, Pete worked on the tail cone.

Having finished the heater cable, I started on mounting the oil cooler. The plans called for machine countersinks on the inside face of one of the parts of the holder for the radiator. It was pretty close in there and the only way I could get a counter sink bit in place was to use my little hand drill. I was quite proud of having come up with such an elegant solution.

There were also a couple of doublers that surround the holes that the line fittings will mount to. Those too were dimpled to be flush on the inside.

And even more countersinking.

Then it all gets riveted together. But wait! What happened to my cleverly countersunk cavities? Crap! I countersunk the wrong part!

I didn't want to countersink this part too, thinking that a whole lot more material than planned on by the ultra-sophisticated computers at Van's had calculated as prudent would be removed by double cutting and that might not be a good thing. Instead, I dimpled the second part. It's not uncommon to dimple a thinner piece of metal where it joins with a thicker, countersunk part, so this felt almost natural.

A line of RTV gets run down the corners of the flanges just prior to putting in the radiator.

Van's suggests blocking off the oil fittings once they're installed to keep from getting dust and stuff into the system. The masking tape wasn't sticking very well, so I helped it out with tie wraps. I tend to the overkill, now and then.

Soon thereafter, it was determined that I had missed squeezing in a couple of rivets. Naturally they were rivets located in a spot that was now impossible to get to with the squeezer, what with the radiator oil fittings in the way. And there was no way I was cutting off those tie wraps!

Out came Gucci, my bright red rivet gun.

Pete had finished up the tail cone by that time, at least to the degree where the stabilator needs to be re-installed. Not being overly keen on that idea, I decided to work on the fuel tank instead. Even through I bought the tank already built, there's still some work to do to get it installed. First, the plans say to attach the fill tub with a big rubber hose and some hose clamps. And oh, by the way: leave a 1/8" gap between the fill tube and the fitting on top of the tank.

The rubber hose is, of course, slightly more than 100% opaque and there was no way to see any gap at all, much less a 1/8" . To solve for that, I marked the location on the side of the tube where it was flush against the hidden edge of the other fitting, then just moved the mark up 1/8".

Genius!

And then the tank gets put into the airplane for the first time. And that went.....

Poorly.

Note the difference between where the bolt thinks the nutplate should be and where the nutplate actually is. It is a not insignificant difference!

This is when I started to sweat. Both set of holes (those in the central spine that the bolts pass through and those in the front of the fuel tank) were drilled by Van's. There is simply no way that I could have screwed this up; something is horribly, horribly wrong. There can be no easy fix for this.

Yeah, I started to sweat.

Meanwhile, Pete calmly whittled away on the cooling duct.

I tried over and over to get the tank to fit, but I just kept coming back to the same conclusion: something is horribly, horribly wrong. I'm going to have to call Van's tech support. That didn't go well the last time I had to do it; the condescending attitude of the support person I talked to had me steamed for days. In an attempt to mitigate the "you must be a complete idiot; we could never do anything that horribly, horribly wrong" attitude, I would have to gather evidence.

That turned out to be both easy to do and a strong conformation of the horrible, horrible problem.

This is the left (looking at the front of the tank) hole:

Here is the right hole. It's just a little more than 44.5cm from the front hole.

This is the right hole (looking aft) on the center section:

Right around 44.2cm. That's not good! It's .3cm to far to the left!

Here's another view of the right hole. If, as in the drawings in the manual, the hole is supposed to be centered between the adjacent rivets, well, you can see where the problem is.

It's that damn Metric system!

So, what do you want to bet that hole would be centered between the rivets if it was .3cm to the right?

The fuel tank fiasco completely ruined my day, and there's at least a 50-50 chance that it will ruin tomorrow too by keeping me awake tonight while I sweat out the question of how Van's intends to fix this. Replacing the center section is certainly not an option - it would require undoing something like 18 months of work.

It was too early to quit working, though, so I decided to finish up the oil radiator job by mounting it to the piece of duct that Pete had been working on. Easy, at the start, with just a couple of holes to get drilled.

A pair of nutplates installed.

Bolted into place.

A couple more holes to drill, some little plastic guiding cones, and some nuts and washers. Piece of cake!

Still too early to quit, so maybe we could get the stab back on after all. I started by cleaning up the loose bundle of wires for the trim motor. Those connectors can be replaced with a different type of connector as part of the imminent avionics installation, but I'n not sure that I'll bother.

From there, it all went down hill. The washers that have to be glued to the stab in order to get them positioned on the hinge bolt fell off as we were sliding the stab into place. I wasted half an hour or so trying to get the washers in place using tweezers and swearing, but it was no use.

I am beginning to lose my faith in tweezers.

We took the stab back off, grabbed some fresh washers that I had ordered the last time I ordered a bunch of "just in case" stuff from Van's, and glued them to the stab.

2 comments:

Wow, Dave, that center section/tank problem looks really bad (as if you wouldn't know that) and I'm sorry you have to work this out with Van's. I had some trouble getting my tank bolted in as well, although the holes were well enough aligned to pull it in after a while. I'll measure to night and see how my holes are aligned but I probably find them reasonably aligned within those existing rivet holes. The way to fix this is to add a back plate on one side of the tank's attach spar and match drill the hole from the center section into the backplate and reinstalling a nutplate in that location. Fortunately it seems to be the inboard hole being off and the tank spar is easier to fix on the inboard than on the outboard side. So be happy that this is fixable and easier than it could be!

I imagine Van's will suggest something similar. They'll probably have me fabricate a new angle piece. What a shame; I just did the service bulletin - that would have been a perfect time to fix this. Now I'm going to have to do it all over again. I wonder how many times I can drill into that tank before ruining it.... It's also going to be a little difficult to move that nutplate closer to the bracket flange.

Post a Comment

N284DG

About Me

Testimonials

"Your writing reminds me of someone you may be too young to appreciate - Gordon Baxter." -- Richard Collins

"I wish.... I could write like you. Oh good God can you paint a picture with words! I have been a fan for years!"

"Said it before. Saying it again. Dave Gamble is one of the greatest writers I've ever read."

"Dave Gamble can wrap words around the story like no other ..."

"I have been reading and totally enjoying your writing for years."

"One of my favorite flying blogs, besides my own of course, is Schmetterling Aviation. I like it mostly because I love to read Dave’s writing. He has a mastery of vocabulary coupled with a great sense of humor that keeps me coming back."

"I solved the problem with help of an excellent builder's web site. Thanks to Schmetterling Aviation's well documented build log."

"I HIGHLY recommend Schmetterling Aviation.com as both thorough and entertaining."

"You have such a great flair for transforming the mundane into an informative, yet humorous read."